Hi,
A friend got me his two Technics SU-V4 amps, both have failed STK modules. I've been reading a lot of bad stuff about those and even worse about the modern counterfeit ones you can buy of a lot of sites.
He really wants to save his amps and I was wondering if it wouldn't be possible to build an equivalent to the modules circuit with discrete components. It seems to have been done for other references (stk-0050 is one of them I believe).
Is it possible to just copy the schematic of the internal circuitry of the stk by using discrete components that can handle a lot more to prevent getting the same problems all over again ?
A friend got me his two Technics SU-V4 amps, both have failed STK modules. I've been reading a lot of bad stuff about those and even worse about the modern counterfeit ones you can buy of a lot of sites.
He really wants to save his amps and I was wondering if it wouldn't be possible to build an equivalent to the modules circuit with discrete components. It seems to have been done for other references (stk-0050 is one of them I believe).
Is it possible to just copy the schematic of the internal circuitry of the stk by using discrete components that can handle a lot more to prevent getting the same problems all over again ?
Hi Depaj,
You might be further ahead adapting another chip to work. Have you checked to see if those chips are available from Panasonic / Technics? If they are, buy them and treat the amplifiers a little more nicely. Failing that, use the chip from one to make the other play again.
If he's going to run the amplifiers hard (they are not suited to that use at all), then buy amplifiers that can handle it. Yamaha Pro amps are extremely good. Old BGW-750 B or C can sound good after a rebuild.
If he has his equipment stacked, he can't do that. Each amp should have 4"~6" clear air above. More if he has it up loud. This is true of all amplifiers.
If he really wants loud, then buy a Carver M-1.5t. That will finish his speakers and his hearing. I think that one is a real 375 wpc.
I can't really offer you any better advice. He has to come to understand these amplifiers are not suited to running at high power, and certainly not stacked as the advertising pictures show.
-Chris
You might be further ahead adapting another chip to work. Have you checked to see if those chips are available from Panasonic / Technics? If they are, buy them and treat the amplifiers a little more nicely. Failing that, use the chip from one to make the other play again.
If he's going to run the amplifiers hard (they are not suited to that use at all), then buy amplifiers that can handle it. Yamaha Pro amps are extremely good. Old BGW-750 B or C can sound good after a rebuild.
If he has his equipment stacked, he can't do that. Each amp should have 4"~6" clear air above. More if he has it up loud. This is true of all amplifiers.
If he really wants loud, then buy a Carver M-1.5t. That will finish his speakers and his hearing. I think that one is a real 375 wpc.
I can't really offer you any better advice. He has to come to understand these amplifiers are not suited to running at high power, and certainly not stacked as the advertising pictures show.
-Chris
Hi Anatech,
A different STK you mean that can handle a little more power to be safe ? The original modules were made by Sanyo apparently but they have been discontinued for a long time and it got almost impossible to get genuine ones. The fake ones tend to fail even with lower bias currents and clamp voltages at moderate volume so...
I don't think he really runs them very hard but I'm sure he's not looking to buy a new amp.
I know I always advice to give any amplifier some room to breathe and I know for sure he does that as well.
A lot of people seem to be trying to save these amps and get confronted with the same problems, wouldn't it be worth the trouble to try and find a solution. I know these aren't the greatest models but I don't think they deserve to just all be thrown away.
A different STK you mean that can handle a little more power to be safe ? The original modules were made by Sanyo apparently but they have been discontinued for a long time and it got almost impossible to get genuine ones. The fake ones tend to fail even with lower bias currents and clamp voltages at moderate volume so...
I don't think he really runs them very hard but I'm sure he's not looking to buy a new amp.
I know I always advice to give any amplifier some room to breathe and I know for sure he does that as well.
A lot of people seem to be trying to save these amps and get confronted with the same problems, wouldn't it be worth the trouble to try and find a solution. I know these aren't the greatest models but I don't think they deserve to just all be thrown away.
I have a V4 that has a dead STK - I am considering replacing both with a STK2058IV or SVI2004 power IC, which would retain new class A operation with much less external throughput pins.
See attached pics
Might consider replacing current stabiliser transistors with resistors - as seen in last pic
See attached pics
Might consider replacing current stabiliser transistors with resistors - as seen in last pic
Attachments
Hi SVI2004A (seems you kind of like this one)
None of these seem to be drop in replacements and they are both 2channel devices, there would have to be some serious re-routing on the board right ? Also what happens to the clamp voltage adjustment ? Is there any guarantee that buying these will get me genuine parts ?
The stk2058IV seem very expensive, is there a guarantee that the SVI2004
None of these seem to be drop in replacements and they are both 2channel devices, there would have to be some serious re-routing on the board right ? Also what happens to the clamp voltage adjustment ? Is there any guarantee that buying these will get me genuine parts ?
The stk2058IV seem very expensive, is there a guarantee that the SVI2004
Hi Depaj,
Mount the new IC to it's own PCB and make the connections between that and the main PCB. Easy-peesy. Either that, or scrap them. You don't have many options.
Don't assume anything that your friend knows or does. Always ask to make sure. There is a reason he has two dead amplifiers. Design is one because they allow those chips to run pretty warm. The fan is very ineffective as well, blowing directly onto the side of the heat sink.
I'm afraid there is no cheap way out of this. So the question now becomes, how much dies he want to keep those amplifiers?
-Chris
Mount the new IC to it's own PCB and make the connections between that and the main PCB. Easy-peesy. Either that, or scrap them. You don't have many options.
Don't assume anything that your friend knows or does. Always ask to make sure. There is a reason he has two dead amplifiers. Design is one because they allow those chips to run pretty warm. The fan is very ineffective as well, blowing directly onto the side of the heat sink.
I'm afraid there is no cheap way out of this. So the question now becomes, how much dies he want to keep those amplifiers?
-Chris
I should of said right away "I know because I asked him", they are on top of a table with nothing above. There actually isn't any fan in this model, sure you aren't mistaking it for the SU-V4X ?
Well it would seem he got really attached to them, sometimes you just can't explain it.
I might be optimistic here but I really don't see why it wouldn't be possible to rebuild the damn stk with discrete components, I would need the values of the resistors and some equivalents for the transistors, Is it possible for someone more experienced than me to get those with an ltspice model ?
Well it would seem he got really attached to them, sometimes you just can't explain it.
I might be optimistic here but I really don't see why it wouldn't be possible to rebuild the damn stk with discrete components, I would need the values of the resistors and some equivalents for the transistors, Is it possible for someone more experienced than me to get those with an ltspice model ?
True... in this case I must say STK8050s do drop for no reason at all... I have a few amps that have done this without ever leaving low volume.
As for clamp V, this is fixed internal in the stereo power packs as is Icq... which is why I’d look into the the 2 3.9K resistor array which will ensure optimal constant current.
These ICs are more reliable than the 8050, and the 2004 has more power and current capability, the transistor chips are somewhat larger than the STK series...
SVI2004C will also work but is not new class A - as the Synchro Bias circuitry was no longer produced in cost cutting. See attachment
As far as I know there are no counterfeits produced for these ICs to date
Attachments
I've seen some people just bypassing the whole power amp section with a different power amp using the same power supply rails but that does go a bit far (even if it might improve sound and stability).
SVI2004A could you send me a little diagram on how you would connect it to the board ? I will probably take your advice and go this way for this particular repair but I still want to try and build something similar tho the original stk but with better components.
I opened one of the 2 stk modules in the amp that has one working channel. This one is definitely a fake but the one that's still working is an original.
I took a picture from the inside and got a schematic from the internal circuit (I don't think I made mistakes but it's still possible). There seem to be some major differences with the schematic of the stk8050 that can be found online (last image). The red crosses are the 2 transistors that have failed.
SVI2004A could you send me a little diagram on how you would connect it to the board ? I will probably take your advice and go this way for this particular repair but I still want to try and build something similar tho the original stk but with better components.
I opened one of the 2 stk modules in the amp that has one working channel. This one is definitely a fake but the one that's still working is an original.
I took a picture from the inside and got a schematic from the internal circuit (I don't think I made mistakes but it's still possible). There seem to be some major differences with the schematic of the stk8050 that can be found online (last image). The red crosses are the 2 transistors that have failed.
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Was trying to make this on pcb software and it heat losing the file
Make a pcb similar (only has to be enough in size to place components and connecting wires.
I have added in the output resistor for existing protect circuit
I have ran with resistored constant current
C1-4 should be close to power ic for stability 120pF
C5,6 50V1uF
Hope this is of some use
Make a pcb similar (only has to be enough in size to place components and connecting wires.
I have added in the output resistor for existing protect circuit
I have ran with resistored constant current
C1-4 should be close to power ic for stability 120pF
C5,6 50V1uF
Hope this is of some use
Attachments
That does seem very doable, have you tried it yourself ?
The owner asked me to put one of the two amps on hold to maybe do some tests on later and to repair the first one with and original but probably fake stk and get it to work as long as possible.
I will look into your option for the second amp but it might have to wait.
Next problem to tackle will be : how to fit the SVI2004A to the heatsink, it looks substantially wider that the 8050 and probably won't fit on there the way it is now except maybe vertically.
The owner asked me to put one of the two amps on hold to maybe do some tests on later and to repair the first one with and original but probably fake stk and get it to work as long as possible.
I will look into your option for the second amp but it might have to wait.
Next problem to tackle will be : how to fit the SVI2004A to the heatsink, it looks substantially wider that the 8050 and probably won't fit on there the way it is now except maybe vertically.
It’s been a while - nearly 18 years since I looked directly in a V4
I will end up doing this myself... I have an absolute mint in box V4 - had it running low background music... it simply just quit... I put it back in its box.... I will bring this out and do this.... I am looking at pcb issues.... pcbexpress will not make single side boards...
More so I had forgotten that poo heatsink centre..... I will get a friend to mill that flat to pcb height... (so it’s still anchored below pcb level) if this is to be done it’s to be done right... not a rush... or a boomerang....
Ppl who have good PCB design software chime in.... SVI is a 16 pin SIP - pin centres 2.5mm
I will see it to successful operation....
I will end up doing this myself... I have an absolute mint in box V4 - had it running low background music... it simply just quit... I put it back in its box.... I will bring this out and do this.... I am looking at pcb issues.... pcbexpress will not make single side boards...
More so I had forgotten that poo heatsink centre..... I will get a friend to mill that flat to pcb height... (so it’s still anchored below pcb level) if this is to be done it’s to be done right... not a rush... or a boomerang....
Ppl who have good PCB design software chime in.... SVI is a 16 pin SIP - pin centres 2.5mm
I will see it to successful operation....
I will make this a fair DIY forum project... I do have a few technics oem second run SVI 2004 chips.... though they’re labeled A variant, they’re C substrate..... I will offer 2 (1 to 2 members that will help SERIOUSLY to the fix.
I require results be shared on this thread /forum
I require results be shared on this thread /forum
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I had good results with allpcb, and they were very fast, maybe try there.
The heatsink is going to be a problem for me, I don't have the tools to do that properly.
Also something that is bothering me, why are pin 5 and 12 ont the svi2004 (labeled as - audio in) connected to the negative power rail through those 2 resistors, shouldn't they be connected to the original pin 14 of the stk ?
The heatsink is going to be a problem for me, I don't have the tools to do that properly.
Also something that is bothering me, why are pin 5 and 12 ont the svi2004 (labeled as - audio in) connected to the negative power rail through those 2 resistors, shouldn't they be connected to the original pin 14 of the stk ?